1. Field of the Invention
The present invention relates to the small compact form of steam generator evolved for marine use where a waste heat source is available and is supplemented by heat from the direct firing of fuel. More specifically, the invention relates to the marine steam generator which fires original fuel for the first radiant heating of water-tubes and combines the products of combustion with waste heat from diesel or gas turbine engines for the second convection heating of superheat tubes.
2. Description of the Prior Art
Steam generation has included the use of a wide variety and combination of heat sources. Bagasse to nuclear fuel pins have had their heat converted into water vapor for driving turbines which, in turn, drive electric generators. Wherever a source of heat can be created, or is produced as a by-product of a power process, the possibility of steam generation--electric production exists.
The art of combining the heat from different sources in marine installations is now before us. The diesel and gas turbine propulsion units on a ship exhaust large quantities of heat which has been wasted in the past. It is an idea whose time has arrived to convert this combined heat to useful electricity. The steam generator is a vital link in this chain of conversion.
The many uses for electricity on shipboard need not be tabulated. The total need may fluctuate but it is continual. With the need accepted, the steam generator is recognized as the standard source of energy to drive the turbo-generator to produce the electricity. The next step is the implementing of the concept of tying the propulsion unit exhaust and the products of combustion of a fuel burner together in the steam generator.
Basically, a steam generator is defined when a heating media is passed around tubes filled with water. The water is vaporized to steam. It is quite common to burn liquid fuel into a heating media of products of combustion. If the problems of regulating this combustion are mastered, and the radiant heat transferred to water, the heat of the products of combustion can be mixed with whatever waste heat is available from propulsion units and additional transfer brought about by convection. Thus we have a broad statement of the basic problem which is now addressed.
The prior art does have, broadly, systems which combine heat from multiple sources to heat water into steam. However, the use of the heat from marine propulsion has not been combined with the convective heat of original fuel combustion for converting water to steam. In briging about this conversion with a steam generating structure the prior art has not solved the marine problem of limiting the size of the vessels containing the liquid collections being vaporized. An efficient contact between convective heating media and the heated water and vapor downstream of the radiant section of the steam generator has not been disclosed. Where superheating of the steam is required, the structure in which the steam is given its additional heating has not been provided with draining provisions when the system must be temporarily shut down.
The foregoing problems, and others, offer a real challenge to the marine form of steam generator. Each solution may not be individually impressive. Yet, taken together the result is a transformation of steam generation into a marine adaptation which is a significant advance in this particular art.